Collecting Sea Trout scale samples

One of the most important parts of the CSTP programme is the collection of sea trout scale samples from 100 rivers, estuaries, coastal waters and further offshore, over the three years of the project. 20 rivers have been targeted for detailed sampling and this protocol is designed to assist anglers in accurate collection of scales for use in subsequent scientific analysis, e.g. stock structuring and distribution (from genetics and scale micro-chemistry) and features such as age and sex composition, life history, growth and survival.

For scale samples the target is 300+ sets of scales per river, to be collected over a two year period, starting in 2009. The samples must be collected in a scientifically unbiased way to ensure that the sample is representative of the stock. This means that fish of all sizes (smallest to largest) and spread throughout the entire angling season should be sampled.

Collect Scale Samples

Anglers are being asked to collect scales and take a length measurements and other relevant information from each sea trout that they catch according to the protocol below. However, for the remainder of the project (summer 2012 onwards), for the rivers in Wales, Northern Ireland, England and Scotland we are not able to accept scales taken from fish returned alive. In those waters scales can only be supplied by anglers from fish that are killed and taken for consumption. Scales from killed or returned fish continue to be acceptable in the Republic of Ireland. The sample required for analysis is about 10-15 scales per fish which should be placed in an individual scale envelope/scale packet.

STEP 1: Request Scale Sampling Pack

If you would like to contribute to the project by collecting scale samples, you will need to request a scale sampling pack. This pack will provide you with scale sample envelopes, tape, plastic knife and instructions on how to correctly take a scale sample.These packs are free of charge and can be ordered in two different ways:

Online

By Phone

Please fill out the form below and we will post out a Scale Sample Pack to you as soon as possible

STEP 2: Taking a sea trout scale sample

Equipment Needed (provided in scale sample pack):

Scale Envelope

Knife/Forcepts

Measuring tape

Pencil

Note: You should only handle live fish with wet hands and ensure measuring device is wet to minimise any potential damage to the fish. Placing a wet hand or damp cloth over the head of the fish while being measured, will calm the fish and allow for the sample to be taken.

Instructions On collecting scale samples

1.

Place the tape on a solid surface, ensuring that it is fully extended.

2.

If the fish is being sampled on the riverbank to return alive, use a plastic sheet or, if suitable, the landing net to protect its flank.

3.

Check to ensure that the tape is fully extended and taut under the fish. Readjust if necessary.

4.

Measure from the tip of the snout to the end of the middle rays of the tail (i.e. fork length). Measurement should be taken in cm, and preferable be taken to the nearest mm but if not possible, the nearest 0.5cm is acceptable.

5.

Record this measurement on the scale sample envelope under ‘Length’.

6.

Fill out all the other details on the envelope including name of fish, weight (kg/g), sex, location of capture, how caught and date of capture.

7.

Ensure that the knife/forceps is totally clean, free from scales, mucus, dirt etc. This is to prevent mixing of scales from other fish.

8.

With the fish calmed, place the knife on the left side just behind the dorsal fin and above the lateral line and run it gently in the direction of the head to loosen the scales. The sample should be about 10-15 scales. Skin sections should not be cut out.

9.

Lift the scale sample with the tip of the knife and transfer to the scale envelop (provided in the sample pack).

10.

The scale sample should be spread across the inside of the envelope to prevent clumping, which can lead to fungal growth and scale degradation of the sample.

11.

Seal the envelope and store in a dry condition as soon as possible to ensure that the scales do not rot.

12.

For live fish i.e. if fish is being returned to water alive, using one finger, rub mucus from the surrounding skin to the sampling area of the fish. This will restore mucus to the area where the scale sample was taken.

Envelopes containing scale samples should not be stored in plastic bags as the scales will rot. Envelopes should be stored in dry conditions as soon as possible to ensure that the scales will remain viable for analysis. If stored under good conditions, the scales will provide genetic material for many decades.

Note: If sampling sea trout in a bag with other sea trout/fish, cross-contamination must be avoided. To prevent this from happening, run the back of the knife over the sampling area in the direction of the tail. This removes any loose scales that may have transferred from the other fish to the skin/mucus of the fish that is to be sampled. Clean the knife thoroughly and follow step 9-12, as detailed above.

STEP 3: Recorded information on each scale sample

For each scale sample taken, information relating to the scale sample must be recorded. These details must be filled out on Scale sample envelopes. These details include:

* Name of the fish:

e.g. finnock, sea trout etc.

* Length:

This is the length of the Sea Trout from the tip of the snout to the end of the middle rays of the tail (i.e. fork length). Measurement should be in cm and recorded to the nearest 0.5cm. State measurement unit used, if length value recorded is not in centimetres.

Weight (if measured):

Weight of the whole fish, preferable weighed on an electronic balance. Weight should be in kg/g and recorded to the nearest gram. State measurement unit used, if weight value recorded is not in kg/g.

Sex:

Which can be found from external or internal examination of the fish.

* Location of Capture:

Record the following information:• Name of tributary/fishery
• River or lake
• Region
• Country

STEP 4: Return scale sample

Store scale sample envelopes in dry conditions to prevent scale deteriorating and rotting. Do not store in a refrigerator or a damp environment. On a monthly basis, please post any scale samples to the following address

For England, Wales, Scotland and Isle of Man:

Feedback

We want to give feedback to fishermen and other interested groups. The CSTP can provide information on scale readings, but responses may take some time because of the volume of analyses to be done. We have already done many talks to angler groups and we are keen to continue this to give updates and here anglers’ views on the project. If you want to have talks given to your association or club please contact the relevant CSTP contact in your area and arrangements will be made for a CSTP person to address your group.